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lar castingspreviously produced.

Patented Sept. 6, 1932 UNITED STATES PATENT OFFICE warren 6. 3012mm, or CLAYTON, MISSOURI, ASSIGNOR 'ro GENERAL STEEL cas'rmes CORPORATION, OF GRANITE CITY, ILLINOIS, A CORPORATION OF DELAWARE HOLD 0B CORE WASH 1 No Drawing.

process and apparatus whereby a substantial amount of gas is intentionally generated by the heat of the molten metal as it approaches the face of the mold or core, whereby acushjion or barrier or buffer is formed between the metal and the face of the core and whereby the face of the casting is cooled rapidly to quickly reduce or eliminate its plasticity.

The main object of my invention is to produce a casting which leaves the mold with a smoother surface than is provided in simi- Mixtures of molasses or glutrin, silica flour and water have beenused heretofore as a wash on cores for castings and have resulted in reasonabl smooth surfaces on castings of small or me ium size. But in the making of the larger castings developed in recent years, particularly in connection with the casting of locomotive beds, locomotive tender underframes, large railway vehicle trucks, etc. it was found that these earlier mixtures did not function as efliciently as desired. Sand would adhere strongly to the surface of the casting, making it rough, unsightly and difficult to clean. I

From microscopic and chemical investigation of the surface of the sand mold next to casting, I concluded that the primary reason for the adhesion of the sand surface and casting was the fact that the sand surface was more or less porous immediately to the rear of the silica wash coating and when this coating was removed by heat or any other reason, or was too thin, the liquid metal, under ferrostatic pressure and high temperature could permeate these voids, and upon cooling, having continuous and intimate contact with the sand, would hold a depth of'sand layer roportional to the penetration of the metal into the sand. This tendency would naturally be increased in the production of the Application fled January 26; 1981. Serial'No. 511,437.

nitrate, ammonium chloride and ammonium sulphate, which are characterized by producing a large volume of gas, when heated, without a residue tending to flux the mold or core surface.

As a result of. numerous experiments I have found the following to be a typical mix- 'ture giving satisfactory resultsbut subject tovariation to suit the circumstances of different metals being cast:

' Parts by Y volume Ammonium nitrate 2 Silica fiour 6 Molasses 1.5 Asbestine 1- Water 4 and the face of the mold or core to prevent the penetration of the interstices of the mold or core by the metal andpreventsthe intimate contact under pressure between the metal. A further action, probably secondary in importance but substantially simultaneous,

is the chilling of the surface of the metal due to the refrigerant effect of the expansion of the gas formed as a result of the application of heat to the wash material.

Castings produced in molds which have been treated as described clean much more readily than those previously produced and have smoother surfaces and sharper contours.

A wash composed of the materials and quantities set forth in the formula given above has given the desired results in the forming of heavy steel castings but it is obvious that the proportions of the ingredients may be varied or that some of the ingredients may be eliminated without departing from the spirit of my invention. If

a substantial volume of gas is generated between the face of the mold or core and the molten metal, the resulting casting will be smoother than those which have been produced by previously known Washes.

I contemplate the exclusive use .of any modifications of the method or apparatus described above which come within the scope of my claims.

I claim:

1. A mold or core wash comprising ammonium nitrate, silica flour, molasses, asbestine'f I material in suspension for giving body to the wash.

In testimony whereof I hereunto afiix my signature this 20th day of January, 1931. WVALTER G. ROEPKE. 

